As my colleague, kamalaboulhosn, posted elsewhere in this thread: "The throughput limitation is 1MB/s per ordering key. The number of unique ordering keys allo

As my colleague, kamalaboulhosn, posted elsewhere in this thread: "The throughput limitation is 1MB/s per ordering key. The number of unique ordering keys allowed on a topic is limited only by what can be represented by a 1KB string, so very high throughput on a topic is still possible." So, it's more of a throughput limit, not a message limit, per key. With small messages, you can get high "TPS". Disclaimer: I work on Cloud Pub/Sub.